After my post on a Linux specific problem and Emacs I feel entitled to bring up another macOS specific issue. This problem is brought to us by Alvaro who explains that it’s possible to combine trackpad scrolling and certain keystrokes that result in a spontaneous font size change in the current buffer. Depending on whether you scroll up or down, the font may become larger or smaller.
The font size changes get triggered when Ctrl is pressed while scrolling. It’s tempting to say it serves him right for using the mouse in Emacs but, as Alvaro says, the MacBook trackpad is especially convenient for scrolling and easy to get used to when in one of those other applications. It’s right there below the keys and so easy to reach with a thumb that one can almost pretend they’re not using the mouse.
For a while, Alvaro solved the problem by simply reloading the file with Ctrl+x Ctrl+v but then someone showed him how to stop Emacs from changing the font sizes to begin with. If you’re having this problem, head over to Alvaro’s post to see to solution. Better yet, keep your hands off the trackpad.